Proceedings of The Physiological Society

Sleep Sleep and Circadian Rhythms (London, UK) (2018) Proc Physiol Soc 42, C26

Poster Communications

Circadian disruption and sleep regulation in mice

A. Fisk1, V. Vyazovskiy1, S. Peirson1

1. Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.

Light is the primary entraining cue for the circadian system, adjusting biological time to the external environment, however it also has direct effects on arousal and sleep. The demands of our modern 24/7 society, with increasing exposure to artificial light at inappropriate times of day, is widely considered to be detrimental to our physiology. Evidence comes from studies using aberrant light/dark (LD) cycles to produce circadian disruption in mouse models. A range of different protocols have been used, including constant light (LL), jet-lag (JL), dim light at night (DLAN), and non-24 hour LD cycles (T-cycles). To date, no detailed comparison of the effects of these different protocols has been conducted, and it remains to be determined whether and how circadian disruption affects sleep regulation. Methods: We used passive infra-red (PIR) sensors to simultaneously measure activity and immobility-defined sleep in wild-type C57BL/6J mice under different protocols, including LL, JL, DLAN and T20 (10h light: 10h dark). We compared the effects of these different protocols on commonly used measures of circadian disruption including periodogram power (Qp), intradaily variability (IV) and interdaily stability (IS), as well on the architecture of immobility-defined sleep. In a separate cohort of C57BL/6J mice (n=7) we examined the effects of 14 days constant light on sleep architecture and EEG. Results: Different LD conditions produced different effects on circadian activity. Whilst IV is increased and IS were decreased under all conditions (n=24, IV ANOVA F(1,20)=28.8 p<0.0001, IS ANOVA F(1,20) = 295.6, p<0.0001) decreases in Qp were only observed under LL and T20 (LL p<0.0001, T20 p=0.0053). All conditions change the distribution of immobility-defined sleep. Furthermore, our preliminary results suggest that constant light acutely increases the amount of sleep in the first day, which results in an altered distribution of EEG slow-wave activity - the established marker of sleep homeostasis. Conclusions: Our data suggests that commonly used protocols exert different effects on sleep and circadian rhythms. These data provide a framework to understand the effects of these protocols on other biological processes such as cognitive functions and physiology.

Where applicable, experiments conform with Society ethical requirements